This invention relates to digital communications networks having permanent virtual connections (PVCs) and switched virtual connections (SVCs) and more particularly to a central management entity that employs a hybrid routing scheme to route cell traffic through such a network.
Within the domain of centrally managed asynchronous transfer mode (ATM) networks, ATM Virtual Channel Connections (VCCs) and Virtual Path Connections (VPCs) have traditionally been routed through the network by the network management entity. This management entity, having complete knowledge of the network topology and the resource utilization within the network, selects routes for individual VCCs through the network based on a series of stored algorithms. These algorithms enable the management entity to bias the routing of VCCs and VPCs in order to maximize network utilization while minimizing cell delay, and to either balance the load throughout the network or to route the connections based on user assigned cost. These centrally managed and routed VCCs are referred to as Permanent Virtual Connections (PVCs).
Switched Virtual Connection (SVC) capabilities are now emerging within these centrally managed ATM networks. These SVC capabilities enable the network elements (also known as switches or nodes) to route VCCs through the network in response to routing requests from attached ATM devices, without the aid of a management entity. The central network management entity can leverage the SVC routing capabilities of these networks for routing centrally managed VCC paths, thereby taking advantage of the improved routing efficiency and performance associated with distributed routing. This is accomplished by enabling the network elements to accept routing requests from management entities. Whenever VCC paths are configured to use SVC routing, the central management entity does not perform any routing whatsoever; it simply sends a routing request to the network element. VCC paths that are routed in this way are known as Switched Permanent Virtual Connections (SPVCs).
The manner in which the SVC capabilities are emerging within networks often leads to networks that are only partially SVC capable. For VCC paths that must traverse both SVC capable network segments and non-SVC capable segments, the management entity is forced to use PVC routing, even across the SVC capable network segment(s). This deficiency results in an inability of the central management system to take advantage of the performance improvements offered by the SVC capable network segments.
The present invention addresses strategies that enable the central management entity to employ both PVC routing and SPVC routing techniques for individual ATM paths.
The strategies employed by this invention overcome the deficiencies noted above by allowing the central management entity to apply the traditional PVC routing algorithms in conjunction with SVC routing capabilities during the routing process of individual ATM paths (VCCs and VPCs).
It is an objective of the present invention to provide a network management entity that employs hybrid routing algorithms to route cell traffic through both PVC and SPVC capable portions of a network.
Therefore, in accordance with the first aspect of the present invention there is provided a method of routing a virtual circuit (VC) through a digital communications network having both Switched Permanent Virtual Circuit (SPVC) capable switching nodes and nonSPVC capable switching nodes, the method comprising: providing a central network management entity having means to route the VC through the non-SPVC capable nodes utilizing Permanent Virtual Circuit (PVC) routing algorithms; and providing SPVC capable nodes for cooperating with the network management entity to route the VC through the SPVC capable nodes utilizing Switched Virtual Circuit (SVC) routing algorithms.
In accordance with a second broad aspect of the invention there is provided a system for routing a virtual circuit (VC) through a digital communications network having both Switched Permanent Virtual Circuit (SPVC) capable switching nodes and non-SPVC capable switching nodes, the system comprising: a central network management entity having means to route the VC through the non-SPVC capable nodes utilizing Permanent Virtual Circuit (PVC) routing algorithms; and means at the SPVC capable nodes to cooperate with the network management entity to route the VC through the SPVC capable nodes utilizing Switched Virtual Circuit (SVC) routing algorithms.